Motor fuels



Patented Get. 26, 1948 FFlC'E MOTOR FUELS William Arthur Partridge and Harold John Alty, Sunbury-on-Thames, England, assignors to Anglo-Iranian Oil Company Limited, London, England, a British corporation No Drawing. Application. February 1, 1946, Serial No. 644,998. In Great Britain February 19,

7 Claims.

1 This invention relates to a process for stabilising motor and aviation fuels containing antiknock reagents.

The use of anti-knock reagents which contain tetra-ethyl lead is widely known and practised in the production of high quality fuels for use in internal combustion engines. In recent years there has been a growing demand for fuels showing still greater resistance to knock and this demand is particularly apparent in the case of aviation fuels. With a view to facilitate the production of these high quality fuels official specifications have appreciably relaxed the lead tolerance. and the inclusion of much larger proportions of anti-knock reagents is now permitted in the manufacture of such fuels.

It is well known that gasoline containing tetraethyl lead, and particularly aviation gasolines which normally contain a higher proportion of the anti-knock reagent than motor gasolines, tend to become unstable on storage and to deposit a white precipitate containing lead. This instability tends to become more marked as the lead content of the fuel rises, and so the relaxation in lead tolerance allowed by the oihclal specifications has accentuated the instability of these leaded fuels.

The reason for this instability has been investigated to some extent and we have found that, among other things, certain sulphur compounds have a marked effect in producing instability. There is some evidence that certain oleflnes also promote instability. The sulphur containing bodies so far found to exhibit this property are elemental sulphur, hydrogen sulphide, carbon disulphide and thiophene. So far as we have ascertained alkyl sulphides and mercaptans do not appear to have any appreciable effect on the stability of aleaded fuel.

We have found that leaded fuels may be stabilised by the addition thereto of minor proportions of alkyl sulphates. I

According to the invention therefore fuels for internal combustion engines which contain tetraethyl'lead as the main anti-knock additive, are stabilised against deterioration in storage by the addition thereto of a small proportion of an alkyl sulphate. I

The proportion of stabilising agent to be added willusually be appreciably less than 1% and, as may be observed from the results given below, satisfactory results are achieved where the fuel contains as little as 0.001% of the additive.

' The alkyl sulphates may be incorporated in thefuel in a number of ways depending on circumstances. to finished fuel, or to any of the constituents of the fuel prior to blending, or to the anti-knock reagent. or incorporated during the blending process, or during the leading operation. Satisfactory results may be attained in any of these ways but it may generally be found most con.- venient to carry out the addition during the leading" operation since this is most likely to ensure an intimate mixing of fuel, anti-knock reagent and additive.

The following examples illustrate the advantages which result from the stabilisation of leaded fuels according to the invention. In each of the examples the fuel used contained 5.5 m1. TEL/I. G. and the storage tests were carried out at 120 F. Criteria of instability under the conditions of test were the times taken in days for the appearance of (a) ,barely visible (trace) (1)) clearly visible (medium) and (0) heavy precipitates. The time taken to form a medium or heavy precipitate is a measure of the stability to be expected in practice. precipitate is not considered to be of importance.

Example I.A C4 aviation alkylate containing lead on storage in the dark, was found to deposit a trace of precipitate after one day and a medium precipitate after 15 days. I

The some fuel with the addition of 0.001% by volume of di-ethyl sulphate deposited a trace of precipitate after 68 days and a medium precipitate after 86 days.

Example II.The fuel used in this example was a sulphur free iso-octane to which thiophene had been added in quantity sufficient to give the fuel a sulphur content of 0.006% by weight.

No. of days for deposition of precipitate Fuel Trace Medium Heavy Unlnhiblted fuel 2 6 Fuel+0.0l% Dlethyl Sul hate. 1 4 Fuel+0.00l% Dlethyl Su phate 1 18 when 0.001% of diethyl sulphate had beenadded to the fuel.

Example IV.The leaded They may, for example, be added fuel in this example The formation of a trace consisted of 90% of sulphur free iso-octane+10% of aCs fraction from C4 aviation alkylate.

fuel containing tetra-ethyl lead. anddialkyl sulphate stabilisingreagent in a proportion within diaikyl sulphate.

Nc.ofdays for deposition the range 0.001% t0.1%. r 1 5 5. A product of manufacture being a gasoline T M H fuel containing tetra-ethyl lead and diethyl sulm phate stabilising reagent in a proportion within g the range 0.001% to 1%. h ffi'efizi 'igaismgjj33:31:; 2 '12 g 6. A process for stabilising a blended gasoline ine] containing tetra-ethyl lead, consisting in the Example V.-The following table indicates readdition of a small proportion of dialkyl sulphate suits of tests made upon stable alkylates and t0 the blended fuelunstable aviation fuel respectively containing sul- A process o producing a t i i e e ed phur as thiophene, CS: and 0.002%8, and the gasoline fuel containing tetra-ethyl lead, consistperiods taken in days for the trace or medium ing in the additionof a small proportion of dialkyl or heavy precipitate to form. sulphate during the blending of the fuel.

' eerie p p Sample Inhibitor jam Trace Medium Heavy smile enemas? sulph thio o 1 1 no p m 1 1 1 3311 11 Sui hate. 0.001 1 3i D m p lSul ate-- 0.001 4 1 130-. Di utyYSulp etc... 0001 4 19 30 Btablealkylate-l-0.005% snlphuras CS; none 1 D0 Dlmethyl Sulphate. 0 001 3 D0 Dlethyl Sulphate--. 0.001 1 3 D0. Di p lSul hate-. 0.001 1 o 10 Do nim lsui ate--. 0.001 a 4 Unstable aviation iuel (0.002%3) none 1 D0 Diethyl Sulphate--. 0001 1 2 Do. Digrop lSul hate 1 s 5 Do Di uty 8111p to.-. 1 a a We claim: WILLIAM ARTHUR PARTRIDGE.

' 1. A process for stabilising gasoline fuels containing tetra-ethyl lead, consisting in the addition to the fuel of a small proportion of dialkyl sulphate. e

2. A process for stabilising gasoline fuels con-'- taining tetra-ethyl lead consisting in the addition to the fuel of appreciably less than 1% of 3.' A process for stabilising gasoline fuels con- HAROLD JOHN ALTY.

40 die of this patent:

taining tetra-ethyl lead, consisting in the addition to the fuel of at least 0.001% by volume of diethyl sulphate.

UNITED STATES PATENTS 

